1. Field of the Invention
The embodiments described herein are related to a multi-band printed circuit board antenna and, more particularly, to a multi-band printed circuit board antenna with a first trace operative in a low frequency band on a first surface of the printed circuit board, and a second trace operative in a high frequency band on an opposing second surface of the printed circuit board.
2. Description of the Related Art
Portable communication devices that communicate with wireless services frequently operate in different frequency bands. Different frequency bands may be used, for example, in different geographical regions, for different wireless providers, and for different wireless services. Pagers, data terminals, mobile phones, other wireless devices and combined function wireless devices therefore often require an antenna or multiple antennas responsive to multiple frequency bands. As an example of a need for multi-band reception and transmission, at least some “world” mobile phones must accommodate the following bands: Global System for Mobile Communication or Group Special Mobile (GSM); Digital Cellular Systems (DCS); and Personal Communication Services (PCS).
Although there are several designs available for external multi-band antennas, conventional portable communication devices house antennas internally or within a device housing on a printed circuit board (PCB). However, conventional PCB antennas are incapable of achieving four bandwidths, such as 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz simultaneously. Further, conventional PCB antennas cannot achieve very low bandwidths, such as 824 MHz, without extending an antenna to interact with further components within a device. One factor causing conventional PCB antennas to be incapable of achieving multi-band capabilities is that traces on conventional PCB antennas include more than four bends (e.g., four 90° turns) forming, for example, a spiral shape. However, the more bends a trace makes, the less effective of a radiator it will be because the trace will interact with material in the PCB and therefore dissipate more energy into the PCB rather than radiating the energy.
FIG. 12 is an example of a conventional system 1200 designed to transfer a ground to a motherboard 1202. Conventional apparatus 1200 comprises two coax cables 1204 and 1205 and an antenna 1206 with a ground end soldered to a ground of a motherboard 1202. In addition, a coax cable ground 1210 is soldered to an edge of the motherboard 1202, thus allowing only a center conductor to make contact with a base of antenna 1206. Conventional apparatus have several problems when connecting, for example, antenna 1206 to a radio 1212. For example, radio 1212 is a secondary PCB having a ground that is poorly connected to motherboard 1202.
Additionally, conventional apparatuses neglect an effect of a coax cable. Therefore, unless there is a balun at the base of the antenna or unless the antenna is fed with a truly differential transmission line, radio frequency currents flow on an outside of the coax cable and radiate, which is undesirable.